SAFE Winch Launching

On Jul 14, 4:34*pm, Gary Emerson wrote:
Just exacly where are you making these tensions measurements????

Are you making them at the weak link??

Are you making these measurements at the winch end of things?

I'd really like to know...

Most people are using a "logger" that works like a GPS logger except
that it measures tension with a load cell and records the data on
flash memory card at a few samples per second for later readout on a
PC. With it's protective padding, It's about the size of a toy
football or a liter soft drink bottle and weighs less than a pound.
It's placed in the winch line near the parachute. I'm not an EE, but
I'm told they are easy to make using off the shelf components - any
"sparky" can build one. It's nice since you can use it on any winch.

You can also measure it at the winch if it's hydraulic or electric or
you use a Running Line Tensiometer (RLT).

A large drum has relatively little rope build-up during a launch so
the effective radius can be estimated pretty closely as a function of
time. With a hydraulic winch, the torque at the drum is directly
related to the oil pressure at the hydraulic motor. With those data,
the rope tension can be calculated to more than good enough accuracy.
It's the same with an electric winch except you measure electrical
values.

No matter how you get it, a tension trace is very useful in diagnosing
problems with a winch - or a winch driver. I'd want to make my own
trace on any winch before I bought it.